/* Sin dependencias externas; adaptable a móviles; contraste alto. */
:root{--bg:#f6f9fc;--fg:#14213d;--card:#fff;--accent:#0b66c2;--line:#cfdceb}
@media (prefers-color-scheme:dark){:root{--bg:#0e1726;--fg:#eaf1fb;--card:#16233a;--accent:#7ec0ff;--line:#2b3d5c}}
*{box-sizing:border-box}
body{margin:0;font:1.05rem/1.6 system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;background:var(--bg);color:var(--fg)}
header,main,footer{max-width:46rem;margin:0 auto;padding:1rem}
header{text-align:center}
header h1{margin:.5rem 0 0;font-size:2.2rem}
header p{margin:.2rem 0}
a{color:var(--accent);text-underline-offset:.15em}
a:focus-visible{outline:3px solid var(--accent);outline-offset:2px}
article{background:var(--card);border:1px solid var(--line);border-radius:1rem;padding:1.2rem;margin:1rem 0}
article h1{font-size:1.6rem;margin-top:0}
h2{font-size:1.15rem;margin:1.4rem 0 .3rem}
footer{text-align:center;font-size:.9rem}